INTERACTION OF H2O AND O2 WITH INTERMETALLIC ALLOYS

The interaction of water vapor and oxygen with Ni 3(Al, Ti) and Ni 3Fe were investigated using Auger electron spectroscopy, X ray photo emission and thermal desorption. These studies showed that water dissociates on Ni 3(Al, Ti) (001) and polycrystalline Ni 3Fe to produce atomic hydrogen above 200 K, while remaining intact when exposed to Ni 3(Al, Ti) (111). In addition, pre adsorbed or co adsorbed oxygen on these surfaces strongly suppresses hydrogen production due to water dissociation. It was shown that adsorbed oxygen reacts with water vapor to produce surface hydroxyls, thus quenching the production of atomic hydrogen. Recent studies revealed an unexpected embrittling effect of boron in Ni 3Al in dry hydrogen. Experiments were proposed to elucidate the different possible roles of boron.